Method of elimination of refrigeration frost



Aug. 17, 1954 R. J. ZELLNER 2,586,497

METHOD OF ELIMINATION 0F REFRIGERATION FROST Filed Sept. 5 1952 3 INVENTOR. ROBERT J. ZELLNER Patented Aug. 17, 1954 METHOD OF ELIlVIINATION F REFRIGERATION FROST Robert J. Zellner, Marinette, Wis., assignor to Ansul Chemical Company, Marinette, Wis., a corporation of Wisconsin Application September 5, 1952, Serial No. 307,981

1 Claim. 1

This invention relates to methods for eliminating and removing frost formed in refrigeration systems.

It is well known that all evaporator coils operated below 32 F. become covered with a layer of frost which reduces the efiiciency of the unit. In many installations this frost is removed periodically with hot Water or other means. Such procedures are very troublesome and labor consummg.

It is thus apparent that continuous removal of frost would be very advantageous and attempts have been made previously to employ solvents for absorbing the frost as it is formed. Such solvents have then been concentrated or regenerated after use by evaporating the water therefrom. Such evaporation requires the use of heat involving heat losses due to the latent heat of water. At best such attempts have been only about 50 per cent eflicient in the recovery of the solvent.

According to the present invention, I have discovered that a number of solvents will dissolve water at the cold temperatures of the evaporator but will not dissolve the water at higher temperatures. It appears possible, therefore, to regenerate the solvent without adding the latent heat of the water. The cost of operation is thus materially reduced.

Further details and advantages of my invention will be apparent from the following specification and appended drawing, wherein Figure 1 is a diagrammatic representation of a refrigeration system provided with means to circulate a selected solvent over the refrigerating coils.

Referring to Figure 1, air is circulated over the cooling coils I supplied through the air openings 2 and 3. Coils I are connected to the refrigerating system through pipes ll. Normally the moisture in the air would freeze out as frost on the cooling coils. However, a spray of solvent 4 supplied through pipe I! passes over the coils and dissolves the moisture. The solvent with its dissolved water collects in the sump 5. The wet solvent is drained from the sump through pipe 15 by pump 5 and passed through the heat exchanger 1, then through pipe l6 into the separator 8 which is hot. The separator may be heated to a predetermined critical temperature by electricity supplied by circuit lll because heat requirements are low or by waste steam, since the temperature is only about 210 F. In the separator the solvent and water are no longer soluble and form two layers, the solvent layer on top and the water layer on the bottom. The separator is maintained above the critical water separation temperature for the given solvent used as will be explained further. The bottom water layer is drawn off through pipe I2 and valve 9. The upper regenerated solvent layer is passed through pipe [4 to the heat exchanger '7 and back through pipe I! over the cooling coils l to pick up more moisture.

In some cases it might be desirable to wash the water supplied through valve 9 with a light hydrocarbon such as naphtha to remove the last traces of solvent. The hydrocarbon can be recovered by distillation. The solvent for this use should be completely miscible with water at evaporator temperatures. Above the critical separation temperature the water should be almost completely free of solvent, but the solvent may contain some water. The solvent should be nontoxic and not too viscous at low temperatures. The water should not easily freeze out of the solvent. A low vapor pressure would reduce solvent losses to the air.

The following solvents listed in Table I have been found suitable for use in my invention:

Table I N-hexyl amine Alpha methyl benzyl monoethanol amine Diethylene glycol n-hexyl ether (hexyl carbitol) Tripropylene glycol isopropylether (Dowanol 2,4,6-trimethyl pyridine (gamma collidine) Water solubility of these solvents was measured by placing weighed quantities of the liquids in tubes which were then sealed. The tubes were cooled until the liquid was clear and then warmed until a faint cloud appeared. This critical temperature was recorded. Below this temperature the water is completely miscible with the solvent.

The amount of solvent soluble in the water determines the losses in the system.

A rough determination of the temperature at which water began to crystallize out of the various solvents was made. Readings were made only at 5 F. intervals and no allowance was made for temperature lag between the bath and the tube or for supercooling of the liquid being tested.

This data is given in Table III:

I have found that of the compounds tested so far, Dowanol 65A (tripropylene glycol isopropyl ether) is particularly advantageous to use. The losses are about 2-2 /2 per cent of the water absorbed. It is colorless and odorless. Boiling point is 496 F. Vapor pressure at 77 F. is 0.01 mm. Hg.

For systems not requiring very low temperature operation, hexyl carbitol (diethyleneglycol heXyl ether) is advantageous as it gives somewhat lower losses of about 0.5 to 0.7 per cent of the water absorbed. It has a slight but not disagreeable odor. Boiling point is about 500 F. Vapor 4 pressure at 20 C. (68 F.) is less than 0.01 mm. Hg.

It is apparent that numerous modifications and changes may be made in utilizing the novel features of my invention which are intended to be included within the scope of the appended claim.

I claim:

The method of continuously removing moisture formed on cooling coils which comprises continuously circulating an organic solvent selected from the group consisting of N-hexyl amine, alpha methyl benzyl monoethanol amine, diethylene glycol n-hexyl ether, tripropylene glycol isopropylether and 2,4,6-trimethyl pyridine, over the coils to dissolve the moisture, said solvent dissolving water at the evaporator temperatures of the cooling coils but not at higher temperatures, continuously collecting the mixture of solvent and water, heating the mixture to form separate liquid layers of solvent and water, separating said layers and recirculating the separated solvent over the cooling coils to absorb additional moisture deposited thereon.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 970,807 Faget Sept. 20, 1910 2,149,990 Cook Mar. 7, 1939 2,343,246 Schechter et al. Mar. 7, 1944 2,557,204 Richardson June 19, 1951 

